In his latest bet on an energy company, activist investor Carl Icahn unveiled a 1.56% stake in drilling company Transocean. The company noted that Icahn also holds a “synthetic long position” and is looking to get regulatory approval to buy up even more shares, potentially making him one of the largest shareholders.

The billionaire investor's total stake amounts to a 3.26% stake in Transocean, which has a market capitalization of nearly $20 billion. According to the release, Icahn is also looking for regulatory approval to potentially buy more than $682.1 million in Transocean stock, which would give him a nearly 5% stake in the company.

Transocean is currently in the process of getting over the Macondo well disaster in the Gulf of Mexico, having recently settled criminal charges for $400 million and agreeing to pay $1 billion in civil charges, according to the FT. Transocean had leased the Deepwater Horizon rig to BP.

Icahn has been interested in several energy companies over the past few years, having made a big move at Chesapeake. The billionaire investor pushed to shake up the board at the troubled natural gas producer. Aubrey McClendon, chief executive of Chesapeake, ultimately bowed to the wishes of Icahn and Southeastern Asset Management, the two largest shareholders, replacing four board members, as my colleague Christopher Helman reported. Icahn was also recently involved in CVR Energy.

Shares in Transocean popped on the news, rallying in early trading on Monday. While the rally partially faded, the stock was still up 1.7% to $54.98 by 12:34 PM in New York.